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revision 1.10 by mlosch, Fri May 15 07:48:47 2009 UTC revision 1.15 by mlosch, Mon Feb 28 16:27:56 2011 UTC
# Line 16  Patrick Heimbach, Chris Hill and Jinlun Line 16  Patrick Heimbach, Chris Hill and Jinlun
16    
17  %----------------------------------------------------------------------  %----------------------------------------------------------------------
18  \subsubsection{Introduction  \subsubsection{Introduction
19  \label{sec:pkg:exf:intro}}  \label{sec:pkg:seaice:intro}}
20    
21    
22  Package ``seaice'' provides a dynamic and thermodynamic interactive  Package ``seaice'' provides a dynamic and thermodynamic interactive
# Line 58  SEAICE requires the external forcing pac Line 58  SEAICE requires the external forcing pac
58  no additional CPP options are required.  no additional CPP options are required.
59  %  %
60  \end{itemize}  \end{itemize}
61  (see Section \ref{sect:buildingCode}).  (see Section \ref{sec:buildingCode}).
62    
63  Parts of the SEAICE code can be enabled or disabled at compile time  Parts of the SEAICE code can be enabled or disabled at compile time
64  via CPP preprocessor flags. These options are set in either  via CPP preprocessor flags. These options are set in either
65  \code{SEAICE\_OPTIONS.h} or in \code{ECCO\_CPPOPTIONS.h}.  \code{SEAICE\_OPTIONS.h} or in \code{ECCO\_CPPOPTIONS.h}.
66  Table \ref{tab:pkg:seaice:cpp} summarizes these options.  Table \ref{tab:pkg:seaice:cpp} summarizes these options.
67    
68  \begin{table}[h!]  \begin{table}[!ht]
69  \centering  \centering
70    \label{tab:pkg:seaice:cpp}    \label{tab:pkg:seaice:cpp}
71    {\footnotesize    {\footnotesize
# Line 127  A package is switched on/off at run-time Line 127  A package is switched on/off at run-time
127  ~ \\  ~ \\
128  %  %
129  Table~\ref{tab:pkg:seaice:runtimeparms} lists most run-time parameters.  Table~\ref{tab:pkg:seaice:runtimeparms} lists most run-time parameters.
130  \input{part6/seaice-parms.tex}  \input{s_phys_pkgs/text/seaice-parms.tex}
131    
132  \paragraph{Input fields and units\label{sec:pkg:seaice:fields_units}}  \paragraph{Input fields and units\label{sec:pkg:seaice:fields_units}}
133  \begin{description}  \begin{description}
# Line 531  widths. For the $u$-equation ($\alpha=1$ Line 531  widths. For the $u$-equation ($\alpha=1$
531    \phantom{=}& \phantom{\frac{1}{A_{i,j}^w} \biggl\{}    \phantom{=}& \phantom{\frac{1}{A_{i,j}^w} \biggl\{}
532    + (\Delta{x}_1\sigma_{21})_{i,j+1}^Z - (\Delta{x}_1\sigma_{21})_{i,j}^Z    + (\Delta{x}_1\sigma_{21})_{i,j+1}^Z - (\Delta{x}_1\sigma_{21})_{i,j}^Z
533    \biggr\}    \biggr\}
534    \intertext{with}  \end{align}
535    with
536    \begin{align}
537    (\Delta{x}_2\sigma_{11})_{i,j}^C =& \phantom{+}    (\Delta{x}_2\sigma_{11})_{i,j}^C =& \phantom{+}
538    \Delta{y}_{i,j}^{F}(\zeta + \eta)^{C}_{i,j}    \Delta{y}_{i,j}^{F}(\zeta + \eta)^{C}_{i,j}
539    \frac{u_{i+1,j}-u_{i,j}}{\Delta{x}_{i,j}^{F}} \\ \notag    \frac{u_{i+1,j}-u_{i,j}}{\Delta{x}_{i,j}^{F}} \\ \notag
# Line 573  Similarly, we have for the $v$-equation Line 575  Similarly, we have for the $v$-equation
575    \phantom{=}& \phantom{\frac{1}{A_{i,j}^s} \biggl\{}    \phantom{=}& \phantom{\frac{1}{A_{i,j}^s} \biggl\{}
576    + (\Delta{x}_1\sigma_{22})_{i,j}^C - (\Delta{x}_1\sigma_{22})_{i,j-1}^C    + (\Delta{x}_1\sigma_{22})_{i,j}^C - (\Delta{x}_1\sigma_{22})_{i,j-1}^C
577    \biggr\}    \biggr\}
578    \intertext{with}  \end{align}
579    with
580    \begin{align}
581    (\Delta{x}_1\sigma_{12})_{i,j}^Z =& \phantom{+}    (\Delta{x}_1\sigma_{12})_{i,j}^Z =& \phantom{+}
582    \Delta{y}_{i,j}^{U}\overline{\eta}^{Z}_{i,j}    \Delta{y}_{i,j}^{U}\overline{\eta}^{Z}_{i,j}
583    \frac{u_{i,j}-u_{i,j-1}}{\Delta{y}_{i,j}^{U}}    \frac{u_{i,j}-u_{i,j-1}}{\Delta{y}_{i,j}^{U}}
# Line 670  where $\Gamma_X$ are the thermodynamic s Line 674  where $\Gamma_X$ are the thermodynamic s
674  diffusive terms for quantities $X=(c\cdot{h}), c, (c\cdot{h}_{s})$.  diffusive terms for quantities $X=(c\cdot{h}), c, (c\cdot{h}_{s})$.
675  %  %
676  From the various advection scheme that are available in the MITgcm, we  From the various advection scheme that are available in the MITgcm, we
677  choose flux-limited schemes \citep[multidimensional 2nd and 3rd-order  recommend flux-limited schemes \citep[multidimensional 2nd and
678  advection scheme with flux limiter][]{roe:85, hundsdorfer94} to  3rd-order advection scheme with flux limiter][]{roe:85, hundsdorfer94}
679  preserve sharp gradients and edges that are typical of sea ice  to preserve sharp gradients and edges that are typical of sea ice
680  distributions and to rule out unphysical over- and undershoots  distributions and to rule out unphysical over- and undershoots
681  (negative thickness or concentration). These scheme conserve volume  (negative thickness or concentration). These schemes conserve volume
682  and horizontal area and are unconditionally stable, so that we can set  and horizontal area and are unconditionally stable, so that we can set
683  $D_{X}=0$. Run-timeflags: \code{SEAICEadvScheme} (default=2),  $D_{X}=0$. Run-timeflags: \code{SEAICEadvScheme} (default=2, is the
684  \code{DIFF1} (default=0.004).  historic 2nd-order, centered difference scheme), \code{DIFF1}
685    (default=0.004).
686    
687  There is considerable doubt about the reliability of a ``zero-layer''  There is considerable doubt about the reliability of a ``zero-layer''
688  thermodynamic model --- \citet{semtner84} found significant errors in  thermodynamic model --- \citet{semtner84} found significant errors in
689  phase (one month lead) and amplitude ($\approx$50\%\,overestimate) in  phase (one month lead) and amplitude ($\approx$50\%\,overestimate) in
690  such models --- so that today many sea ice models employ more complex  such models --- so that today many sea ice models employ more complex
691  thermodynamics. The MITgcm sea ice model provides the option to use  thermodynamics. The MITgcm sea ice model provides the option to use
692  the thermodynamics model of \citet{win00}, which in turn is based  the thermodynamics model of \citet{win00}, which in turn is based on
693  on the 3-layer model of \citet{sem76} and which treats brine  the 3-layer model of \citet{sem76} and which treats brine content by
694  content by means of enthalpy conservation. This scheme requires  means of enthalpy conservation; the corresponding package
695  additional state variables, namely the enthalpy of the two ice layers  \code{thsice} is described in section~\ref{sec:pkg:thsice}. This
696  (instead of effective ice salinity), to be advected by ice velocities.  scheme requires additional state variables, namely the enthalpy of the
697    two ice layers (instead of effective ice salinity), to be advected by
698    ice velocities.
699  %  %
700  The internal sea ice temperature is inferred from ice enthalpy.  To  The internal sea ice temperature is inferred from ice enthalpy.  To
701  avoid unphysical (negative) values for ice thickness and  avoid unphysical (negative) values for ice thickness and
702  concentration, a positive 2nd-order advection scheme with a SuperBee  concentration, a positive 2nd-order advection scheme with a SuperBee
703  flux limiter \citep{roe:85} is used in this study to advect all  flux limiter \citep{roe:85} is used in this study to advect all
704  sea-ice-related quantities of the \citet{win00} thermodynamic  sea-ice-related quantities of the \citet{win00} thermodynamic model.
705  model.  Because of the non-linearity of the advection scheme, care  Because of the non-linearity of the advection scheme, care must be
706  must be taken in advecting these quantities: when simply using ice  taken in advecting these quantities: when simply using ice velocity to
707  velocity to advect enthalpy, the total energy (i.e., the volume  advect enthalpy, the total energy (i.e., the volume integral of
708  integral of enthalpy) is not conserved. Alternatively, one can advect  enthalpy) is not conserved. Alternatively, one can advect the energy
709  the energy content (i.e., product of ice-volume and enthalpy) but then  content (i.e., product of ice-volume and enthalpy) but then false
710  false enthalpy extrema can occur, which then leads to unrealistic ice  enthalpy extrema can occur, which then leads to unrealistic ice
711  temperature.  In the currently implemented solution, the sea-ice mass  temperature.  In the currently implemented solution, the sea-ice mass
712  flux is used to advect the enthalpy in order to ensure conservation of  flux is used to advect the enthalpy in order to ensure conservation of
713  enthalpy and to prevent false enthalpy extrema.  enthalpy and to prevent false enthalpy extrema. %
714    In order to use the \code{seaice}-package with the more sophisticated
715    thermodynamics of \code{thsice}, compile both packages and turn both
716    package on in \code{data.pkg}; see an example in
717    \code{global\_ocean.cs32x15/input.icedyn}.
718    
719  %----------------------------------------------------------------------  %----------------------------------------------------------------------
720    
# Line 769  Diagnostics output is available via the Line 780  Diagnostics output is available via the
780  Available output fields are summarized in  Available output fields are summarized in
781  Table \ref{tab:pkg:seaice:diagnostics}.  Table \ref{tab:pkg:seaice:diagnostics}.
782    
783  \begin{table}[h!]  \begin{table}[!ht]
784  \centering  \centering
785  \label{tab:pkg:seaice:diagnostics}  \label{tab:pkg:seaice:diagnostics}
786  {\footnotesize  {\footnotesize
# Line 834  Table \ref{tab:pkg:seaice:diagnostics}. Line 845  Table \ref{tab:pkg:seaice:diagnostics}.
845    
846  %%% Local Variables:  %%% Local Variables:
847  %%% mode: latex  %%% mode: latex
848  %%% TeX-master: "../manual"  %%% TeX-master: "../../manual"
849  %%% End:  %%% End:
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